I have been doing closed transfers under CO2 with the conical. 2 PSI in top speeds up the process, my Blichmann is rated for 3 PSI. That is like having a 54+ inch column on top of the beer. The second 5 gallons is where it is noticeable if you do 10 gallon batches.
The Blichmann has a pop off weight, so I am safe. Watch that the regulator pressure does not creep up.
I pull the airlock, and have a barbed fitting that goes into the stopper, the fitting has some tubing with a gas fitting that goes on the CO2 line swivel fitting.